Increased intraocular pressure is accepted as a primary etiologic factor for the atrophy of the optic nerve head and visual field defects of high-tension glaucoma. Other factors must be present to explain these findings in low-tension glaucoma. One of the current theories is that low-tension glaucoma is the result of decreased optic nerve perfusion on the basis of vascular disease or other factors such as altered blood viscosity. This study compared the non-invasive vascular profiles, coagulation tests, and rheological profiles of 46 consecutive cases of low-tension glaucoma with 69 similarly unselected cases of high-tension glaucoma and 47 age-matched controls. Despite the multifactorial approach and the use of previously validated objective tests, no significant group differences were detected with any of the above investigations. If vascular disease is important in the etiology of low-tension glaucoma, then it must be localized or vasospastic since this study does not support the concept of a generalized vascular etiology, either of an atheromatous or hyperviscous nature, for the genesis of low-tension glaucoma.